JP2000251321A - Rewrite type optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cross-interlacing at the time of rewriting by eliminating the conduction of the heat generated by a land recording layer or groove recording layer to an adjacent land recording layer or groove recording layer by separating a recording layer into land recording layers provided on a land and groove recording layers provided on a groove part. SOLUTION: The side walls of the land part R are formed into reverse tapered walls 10 (so that the interval between both side walls become gradually narrow to the lower part) or vertical walls 20 (so that the interval between both the side walls is constant in width from the upper end to the lower end), thereby a recording layer separation part is provided. A groove recording layer 3a is filmed on the groove part G by a collimation sputtering method or long sputtering method and a land recording layer 3b is filmed on the land part R. Consequently, the recording layer is not filmed on the reverse tapered walls 10 at all and the recording layer filmed on the vertical walls 20 becomes discontinuous, so that the groove recording layer 3a and land recording layer 3b can be separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk, and more particularly to a rewritable optical disk capable of erasing and rewriting information.

[0002]

2. Description of the Related Art There is an optical disk called a rewritable optical disk in which once written information can be erased and new information can be written. As an example of such an optical disk, there is a CD-RW, in which pits whose information is rewritten by utilizing the fact that the recording layer reversibly changes between a crystalline state and an amorphous state when irradiated with laser light. To form. In a rewritable optical disk, such a change in the state of the recording layer is detected by a pickup as a difference in reflectance, and the written information is read.

FIG. 8 is a diagram illustrating a general configuration of such a rewritable disc. The illustrated rewritable optical disk has a guide groove formed on a substrate such as polycarbonate, and a recording layer is provided thereon. The guide groove is for obtaining a tracking signal when reading or rewriting information. In an optical disc, a laser beam of a pickup is generally incident from the substrate side at the time of reading, and the uneven portion formed by the guide groove is
The portion farther to the pickup side (the convex portion as viewed from the recording layer side) is called a land portion, and the one closer to the pickup side (the concave portion as viewed from the recording layer side) is called a groove portion. Many pits and recording marks for recording information are provided in groove portions.

In recent years, CDs (Compact) have been developed.
Disc (DVD) having a larger recording capacity than disc (digit)
al video disc),
There is also a rewritable optical disk having this configuration. In a DVD rewritable optical disk, the size of a pit or the interval (track pitch) between a land portion or a groove portion (also referred to as a track) where a pit is provided is reduced.

[0005] In the rewritable optical disk described above, when information is read out or rewritten from the optical disk, if the laser beam is larger than the track pitch, a phenomenon occurs in which an adjacent track is affected. This phenomenon is called crosstalk when the information written on the adjacent track interferes when reading information, and is called cross erase when the information written on the adjacent track is erased when erasing for rewriting. . Among such phenomena, crosstalk can be reduced by setting the depth of the guide groove, that is, the step between the land and the groove according to the wavelength and the refractive index of the laser beam.

[0006]

However, in the case of cross-erase, in addition to the laser beam being directly applied to the adjacent track, heat generated in the recording layer by the applied laser beam propagates to the adjacent track. It is also caused by things. For this reason, cross-erase is also called thermal crosstalk, and there is a method of reducing the cross-erase by taking a sufficiently large step between the land portion and the groove and increasing the distance over which heat propagates. But,
For the recording layer, a metal film having high thermal conductivity such as GeSbTe or AgInSbTe is used. For this reason, it is also difficult for such a method to sufficiently suppress the heat propagation of the recording film.

Further, in order to prevent cross-erase on an optical disk having a small track pitch, it is necessary to use a laser beam having a shorter wavelength for rewriting information.
At present, a DVD having a recording capacity of 4.7 GB has a wavelength of 65 GB.
A 0/635 nm red laser is used. However, if an optical disk having a larger recording capacity is put to practical use in the future, a blue laser having a wavelength of 410 nm will be required. Such a blue laser has a 30 m
Although the condition of obtaining the output of W (a value calculated based on the temperature required for causing the recording layer to undergo phase transition) is being satisfied, there is a problem in terms of life. For this reason, it is desired that the rewritable optical disk be configured so that information can be written with lower energy and the laser light source can have a longer life.

The present invention has been made in view of the above points, and has as its first object to provide a rewritable optical disk capable of reducing cross-erase at the time of rewriting. A second object of the present invention is to provide a rewritable optical disk which can be rewritten with a smaller laser output.

[0009]

The above-mentioned problems can be solved by the following means. That is, according to the first aspect of the present invention, the guide groove formed on the surface, the land portion which is a convex portion formed by the guide groove, the groove portion which is a concave portion, and the land portion and the groove portion are formed. Provided,
A recording layer on which information can be rewritten by irradiating light; and a land recording layer provided on the land portion and a groove recording layer provided on the groove portion among the recording layers Are separated from each other.

[0010] With this configuration, heat generated in the land recording layer or the groove recording layer does not propagate to the adjacent land recording layer or the groove recording layer.

According to a second aspect of the present invention, in the separation of the land recording layer and the groove recording layer, a recording layer separation portion having no recording layer is provided on a side wall between the land portion and the groove portion. It is characterized by what is done.

With this configuration, there is no medium for transmitting heat between the land recording layer and the groove recording layer, so that the heat generated in the land recording layer or the groove recording layer can be reliably transferred to the adjacent land recording layer or groove. Propagation to the recording layer can be prevented.

Further, the invention according to claim 3 is characterized in that the recording layer separating portion is formed by making a side wall of the land portion reversely tapered or vertical.

With this configuration, the recording layer separation section can be automatically provided by forming a film by a sputtering method in which the side wall has a reverse taper or a vertical direction, and the directivity of sputtered particles is high with respect to a vertical land layer. .

The invention according to claim 4 is characterized in that the land recording layer is further removed.

With such a configuration, in an optical disc of a type in which information is recorded only in the groove portion, the distance between the recording layers where there is no member for transmitting heat is sufficiently long, and the heat generated in the groove portion is not adjacent to the recording layer. Propagation to the groove portion of the matching track can be reliably prevented.

Further, the invention according to claim 5, wherein the recording layer has a first recording layer and a second recording layer provided on the first recording layer, and a land of the first recording layer. The recording layer is removed, and the second recording layer is formed continuously.

According to this structure, the distance between the first recording layer and the region where there is no member for transmitting heat becomes sufficiently long, and the heat generated in the groove portion is transmitted to the groove portion of the adjacent track. Can be reliably prevented.
In the second recording layer, the distance between the recording layers to which the heat is applied is sufficiently large, and the generated heat can be prevented from being transmitted to the recording layers of the adjacent tracks. In addition, by providing the two recording layers as described above, it is possible to secure a large area of the recording layer for writing information while preventing heat from being propagated.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 3 of the present invention will be described below. (Embodiment 1) The rewritable optical disk of Embodiment 1 (hereinafter simply referred to as an optical disk) has a guide groove formed on the surface, and a land portion and a groove portion are formed by the guide groove. Each of the land portion and the groove portion has a recording layer in which information can be rewritten by irradiating a laser beam. Among the recording layers, a land recording layer on the land portion and a groove recording layer on the groove portion are provided. Are separated from each other.

In the first embodiment, the land recording layer and the groove recording layer are separated from each other by providing a recording layer separating portion having no recording layer on the side wall between the land portion and the groove portion. Embodiment 1 shows such a configuration in FIG.
This is applied to an optical disc provided with pits (indicated by recording marks) in both the land portion and the groove portion as shown in FIG.

FIG. 2 is a view for explaining the optical disk of the first embodiment, and is a cross-sectional view of the optical disk cut perpendicular to the length direction of the guide groove, similarly to FIG. In FIG. 2, FIG. 2 (a) shows a configuration in which a recording layer separating portion is formed by making a side wall of a land portion into an inversely tapered shape (a gap between both side walls gradually narrows downward).
In (b), the recording layer separation portion is provided by making the side wall of the land portion vertical (the interval between both side walls is a constant width from the upper end to the lower end). In addition, FIG.
Each of the configurations shown in FIGS. 1A and 1B is a polycarbonate substrate 1 provided with a land portion R and a groove portion G.
A recording layer (groove recording layer) 3a provided on the groove portion G, a recording layer (land recording layer) 3b provided on the land portion R, a groove recording layer 3a, and a land recording layer 3b.
And a protective layer 4 provided thereon.

In the first embodiment, the groove recording layer 3a and the land recording layer 3b are formed by a method such as collimation sputtering or long throw sputtering using a film forming material such as GeSbTe or AgInSbTe. Such a film forming method is known to have a very high directivity of sputtered particles. Therefore, when the recording is performed on the land portion R having the side wall (reverse taper wall) 10 having the reverse taper shape, the recording layer is not formed on the reverse taper wall 10 at all. For this reason, the adjacent land portions R
Thus, a shape in which the groove recording layer 3a and the land recording layer 3b are separated between the groove portion G and the groove portion G is realized (FIG. 2A).

In the first embodiment, the groove recording layer 3a and the land recording layer 3b are formed on the land R having the vertical side wall (vertical wall) 20 by a method such as collimation sputtering or long throw sputtering. Then, the recording layer formed on the vertical wall 20 is discontinuous so that heat cannot be transmitted. Even in such a configuration, the groove recording layer 3a, between the adjacent land portion R and the groove portion G,
A shape in which the land recording layer 3b is separated is realized (FIG. 2).
(B)).

Next, the reverse taper wall 10 or the vertical wall 2
The step of forming a substrate having 0 will be described. 3 and 4
FIG. 3 is a diagram for explaining a step of forming the substrate 1 used in the first embodiment. Note that, here, only the step of forming the substrate having the land portion R of the reverse tapered wall 10 shown in FIG. 2A will be illustrated. 3 and 4 are exaggerated for ease of understanding.

In the steps shown in FIGS. 3 and 4, first, a photoresist 30 is applied on the glass substrate 100 (FIG. 3).
(A)). The glass substrate 100 is soda lime glass having a thickness of about 10 mm. Subsequently, lands, grooves and pits (not shown) are formed on the photoresist 30 by a process called laser cutting. Laser cutting is performed using a laser cutter, which is an optical disk drive, for He-Cd, He-Ne,
The photoresist 30 is exposed using a short wavelength gas laser such as Ar as a light source.

After this exposure, the photoresist 30 is developed. At this time, there is a close relationship between the shape of the photoresist 30 after development and the exposure conditions, and the exposure amount, the exposure time, and further the development conditions are adjusted so that the side wall shown in FIG. It is possible to obtain the resist 30 having a reverse taper (a forward taper when viewed from the groove side). In the first embodiment, such a shape of the resist 30 is obtained by setting the exposure condition of laser cutting to overexposure. In the first embodiment, the photoresist 30
, A negative resist is used.

Next, a conductive film 35 of, for example, nickel is deposited on the exposed and developed resist 30 (FIG. 3C). Then, thick film electroforming is performed using the surface of the conductive film 35 as a cathode. Thick film 4 formed as a result of this thick film electroforming
When 0 becomes about 0.3 mm thick (FIG. 3D), the resist 30 is peeled off and washed to obtain a mold for an optical disk substrate.

A metal plate 50 is lined on the back surface of the obtained mold to complete the stamper shown in FIG. Using this stamper, land, groove,
Further, pits and the like are transferred. In the first embodiment, the substrate is formed by injection molding. For this reason, as shown in FIG. 3F, polycarbonate is poured into an injection mold 41 using a stamper, and FIG.
Is obtained.

In the steps described above, when the angle of the reverse taper of the stamper is steep, it becomes difficult to remove the substrate from the stamper after the injection step. For this reason, when exposing the resist 30, the laser cutting conditions are set so that the angle of the reverse taper is 1 to 2 degrees, and in accordance with this, it is possible to remove the substrate material from the stamper before the substrate material is completely cooled. is necessary.

In the description of FIGS. 3 and 4, FIG.
As described above, only the production of the substrate having the inverted tapered wall 10 in the land portion has been described. However, by adjusting the conditions for laser cutting of the resist 30, the resist 3
It is also possible to make the side walls of 0 vertical and to make a substrate with vertical walls 20. Further, such a condition can be realized by suppressing the exposure amount as compared with the case where a reverse taper is formed.

According to the first embodiment, the substrate 1
No heat is transmitted between the land recording layer 3b and the groove recording layer 3a, or the transmission efficiency is significantly reduced. For this reason, the heat generated by the laser beam applied to the land recording layer 3b or the groove recording layer 3a causes the adjacent land recording layer 3b or the groove recording layer 3a to emit heat.
Can be prevented from being transmitted. Therefore, when erasing information written on the optical disk, the temperature of a portion other than the portion irradiated with the laser beam does not undergo phase transition, and cross-erase hardly occurs.

Further, since the heat generated in the recording layer is difficult to propagate, the heat stays in the irradiated area and the temperature of the recording layer can be efficiently increased. Therefore, information can be rewritten even when the power of the laser is relatively small, and the life of the laser light source can be further extended.

Further, in the first embodiment, the reverse tapered wall 10,
By forming a recording layer on the land portion R having the vertical wall 20, the land recording layer 3b and the groove recording layer 3a are formed.
Are separated. For this reason, the land recording layer 3b and the groove recording layer 3a can be separated without adding a mask step, and the steps can be simplified.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described. In the second embodiment, a rewritable optical disc (DV) in which information is recorded only in the groove recording layer is used.
D-RW), in which the land recording layer and the groove recording layer are separated, and then the land recording layer is removed.

FIG. 5 is a diagram for explaining the configuration of the optical disk of the second embodiment, and is a cross-sectional view of the optical disk cut perpendicularly to the length direction of the guide groove. In the configuration shown in the figure, the substrate 1 has a groove portion G on which the groove recording layer 3a is provided.
And a land portion R having a vertical wall 20, and the land portion R has no land recording layer. Further, a protective film 4 is provided on such a substrate 1.

FIGS. 6A to 6C are views for explaining steps of manufacturing the optical disk shown in FIG.
In this step, first, the recording layers become discontinuous at the vertical wall 20 shown in FIG. 2B by the steps described with reference to FIGS. 3 and 4, so that the land recording layer 3b and the groove recording layer 3 are formed.
Create a configuration that separates a. Then, a protective film 4 is further formed on this structure (FIG. 6A). This recording film 4
May be formed by a general method such as a normal sputtering method or a vacuum evaporation method.

Next, CMP (chemical mec)
The land recording film 3b is removed by polishing by a mechanical polishing method (FIG. 6B). At this time, the protective film on the groove portion G serves to prevent the groove recording layer 3a from being polished by CMP. After the polishing is completed, a protective film is formed again (FIG. 6).
c), the shape of the optical disk shown in FIG. 5 is completed.

According to the second embodiment, a region where the recording layer is not formed between the groove portions G where the information is written can be sufficiently secured. Therefore, it is possible to reliably prevent the heat generated by irradiating the target groove portion G with the laser beam from affecting the adjacent groove portion G,
The effect of preventing cross-erase can be further enhanced. Also, from this, in the second embodiment,
It is not necessary to completely remove the film formed on the side wall. Therefore, it is not necessary to prepare the substrate 1 in which the land portion R has an inversely tapered wall, and it can be implemented relatively easily.

Third Embodiment Next, a third embodiment of the present invention will be described. The third embodiment is directed to a rewritable optical disk (DVD-RAM) in which information is recorded on both a land portion and a groove portion.
Then, a first recording layer and a second recording layer provided on the first recording layer are provided on the substrate, and while the land recording layer of the first recording layer is removed, the second recording layer is continuously formed. To form.

FIG. 7 is a view for explaining the configuration of such an optical disk according to the third embodiment, and is a cross-sectional view of the optical disk cut perpendicularly to the length direction of the guide groove. In the configuration of FIG. 7, a recording layer 3c is further provided on the entire surface of the optical disk according to the second embodiment described above. In the recording layer 3c, information is recorded only in a portion corresponding to an upper portion of the land portion R.
For this reason, the recording layer 3c is referred to as a land recording layer 3c. Then, a protective film 4 is further provided on the land recording layer 3c to complete the shape of the optical disc of the third embodiment.

According to the third embodiment, a high cross-erase prevention effect similar to that of the second embodiment can be obtained for the groove recording layer 3a. In the land recording layer 3c as well, although the recording layer is continuous, the interval between the portions where information is recorded is one track (DV).
(0.74 μm in D), a sufficient cross-erase prevention effect can be obtained.

The present invention is not limited to the above embodiment. For example, in the first and second embodiments, the land recording layer and the groove recording layer are separated from each other by making the side wall of the land portion a vertical wall or an inversely tapered wall. However, the shape of such a side wall is not limited to a vertical wall or an inversely tapered wall, but may be any shape as long as the recording film is separated in a self-aligned manner.

[0043]

The present invention described above has the following effects. In other words, according to the first aspect of the invention, the generated heat does not propagate to the adjacent land recording layer or groove recording layer. Therefore, when rewriting information written in a predetermined portion of the recording layer, heat generated by the laser beam applied to the predetermined portion does not affect information recorded in another portion. Therefore, the invention according to claim 1 can provide a rewritable optical disk capable of reducing cross-erase at the time of rewriting.

Further, according to the first aspect of the present invention, it is possible to prevent the heat applied to the recording layer from being transmitted to other portions, and to cause the recording layer to undergo phase transition with a small power. Therefore, the first aspect of the present invention can provide a rewritable optical disk that can be rewritten with a smaller laser output.

According to the second aspect of the invention, the heat generated in the land recording layer or the groove recording layer is reliably prevented from being transmitted to the adjacent land recording layer or the groove recording layer. For this reason, it is possible to provide a rewritable optical disc that can more reliably reduce cross-erase at the time of rewriting.

According to the third aspect of the present invention, the recording layer separating section can be automatically provided by sputtering, and the configuration in which the land recording layer and the groove recording layer are separated can be realized relatively easily.

Further, according to the present invention, the heat generated in the groove portion can be reliably prevented from being transmitted to the groove portion of the adjacent track, and the optical disc in which information is recorded only in the groove portion is provided. It is possible to provide a rewritable optical disk capable of more reliably reducing cross-erase at the time of rewriting.

According to a fifth aspect of the present invention, there is provided a rewritable optical disc having a good recording density which can secure a large area of a recording layer for writing information and can surely reduce cross-erase at the time of rewriting, while preventing heat propagation. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical disc to which a configuration according to a first embodiment is applied;

FIG. 2 is a cross-sectional view for explaining the optical disc of the first embodiment.

FIG. 3 is a diagram for explaining a step of forming a substrate used in the first embodiment.

FIG. 4 is another view for explaining the step of manufacturing the substrate used in the first embodiment.

FIG. 5 is a cross-sectional view illustrating an optical disc according to a second embodiment.

FIG. 6 is a diagram for explaining a step of manufacturing the optical disc shown in FIG.

FIG. 7 is a cross-sectional view illustrating an optical disc according to a third embodiment.

FIG. 8 is a diagram illustrating a general configuration of a rewritable disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 3a Groove recording film 3a Land recording film 4 Protective film 10 Reverse taper wall 20 Vertical wall 30 Resist 35 Conductive film 40 Thick film 41 Injection mold 100 Glass substrate

Claims (5)

[Claims] 1. A guide groove formed on a surface, a land portion that is a convex portion generated by the guide groove, a groove portion that is a concave portion, and provided on the land portion and the groove portion, and light is provided. A recording layer on which information can be rewritten by being irradiated, and a land recording layer provided on the land portion and a groove recording layer provided on the groove portion of the recording layer. A rewritable optical disk characterized by being separated. 2. The method according to claim 1, wherein the land recording layer and the groove recording layer are separated by providing a recording layer separation part without the recording layer on a side wall between the land part and the groove part. The rewritable optical disk according to claim 1. 3. The rewritable optical disk according to claim 2, wherein the recording layer separation section is formed by making a side wall of the land section taper or perpendicular. 4. The rewritable optical disk according to claim 3, wherein said land recording layer is further removed. 5. The recording layer according to claim 1, wherein the recording layer comprises a first recording layer,
And a second recording layer provided above the recording layer, wherein the land recording layer of the first recording layer is removed, and the second recording layer is formed continuously.
4. The rewritable optical disk according to any one of items 1 to 3.